1. Field of the Invention
The present invention relates in general to a method for transforming video data comprising an interest region by wavelet transform signal processing. In particular, the present invention relates to a method for controlling the difference between the region of interest (ROI) and the region of no interest (non-ROI) of a video surveillance data by wavelet transform signal processing.
2. Description of the Related Art
Video surveillance is used to monitor images of a specific region. The conventional process to transform the video surveillance data is described as follows. First, an original image is analyzed to generate spectrums with different frequency, and then the information in the region of interest (ROI) and the region of no interest (non-ROI) in each spectrum is obtained. The region of interest (ROI) is defined according to the parameters of the video surveillance system, for example, the moving objects in the original image, the objects with predetermined temperature, and objects with predetermined shapes, all relating to the monitored targets.
FIG. 1 shows an original image 10 caught by the video surveillance system. The region 12 is the region of interest (ROI). The original image is analyzed to generate spectrums with different frequency. Then, the coordinate of the ROI is calculated according to the location of the ROI in the original image. FIG. 2 is a diagram of the original image 10 transformed by the wavelet transform signal processing. In FIG. 2, each block (20˜129) has an independent frequency band, and the frequency of the frequency band is decreased in order from block 20 to block 29. The oblique lines in the blocks (20˜29) represent the information of the ROI in the original image 10. In the spectrums transformed by wavelet transform signal processing, the lower frequency information represents the indistinct images in the original image 10, which records the contour of the original image 10, and the higher frequency information represents the tiny images in the original image 10, which are the shadow or the spots in the original image 10.
After the wavelets transform signal processing, the data is transformed by bit plane coding. FIG. 3A shows the original bit plane of the image. There are two regions in the original bit plane, one is the ROI of the bit plane, and the other is the region of the non-ROI bit plane. In FIG. 3B, the bit plane coding raises the resolution of the ROI region to emphasize the image of ROI. The data in the non-ROI region with little significance is recorded with few resources or abandoned. The bit plane coding is used to decrease the data volume of the image data. Therefore, the monitored image will be clearer in the same hardware equipment. Afterward, the image data is encoded to a specific form as JPEG2000 for example to record.
However, in wavelets transform signal processing, if the region of interest is too large or the bit rate is too slow, the non-ROI region of the image will disappear and deteriorates the display of the image as shown in FIG. 4.